This is Shane's Acquisition Understander packaged as a Zope product. Also see http://zope.org/Members/chrisw/showaq

The AcquisitionUnderstander product makes the command "showaq" available to Zope. You may append "showaq" to any URL to get a graphical representation of the acquisition paths involved. The graph, if read from top to bottom, shows the exact search order implemented by Acquisition.c.

The advantage of this product over the external method approach is that it also works when PythonScripts and PageTemplates are involved.

Try e.g.
http://localhost:8080/Examples/ShoppingCart/showaq
http://localhost:8080/Examples/ShoppingCart/Control_Panel/showaq
http://localhost:8080/Examples/ShoppingCart/Control_Panel/index_html/showaq

The "showaq" command is protected by the "Use Acquisition Understander" permission.

To install untar the archive into your Products directory and restart Zope.